What Is Air Duct Cleaning?

Duct cleaning generally refers to the cleaning of various heating and cooling system components of forced air systems, including the supply and return air ducts and registers, grilles and diffusers, heat exchangers, heating and cooling coils, condensate drain pans (drip pans), fan motor and fan housing, and the air handling unit housing If not properly installed, maintained, and operated, these components may become contaminated with particles of dust, pollen or other debris. If moisture is present, the potential for microbiological growth (viz. mold) is increased and spores from such growth may be released into the home's living space. Some of these contaminants may cause allergic reactions or other symptoms in people if they are exposed to them. If you decide to have your heating and cooling system cleaned, it is important to make sure the service provider agrees to clean all components of the system and is qualified to do so. Failure to clean a component of a contaminated system can result in re-contamination of the entire system, thus negating any potential benefits.

Deciding Whether or Not to Have Your Air Ducts Cleaned

You should consider having the air ducts in your home cleaned if:

If you choose to get your ducts cleaned, how do you check to see if you got your money's worth?  

A thorough visual inspection is the best way to verify the cleanliness of your heating and cooling system. Some service providers use remote photography to document conditions inside ducts. All portions of the system should be visibly clean; you should not be able to detect any debris with the naked eye. Has the service provider adequately demonstrated that duct work and plenums are clean? (Plenum is a space in which supply or return air is mixed or moves; can be duct, joist space, attic and crawl spaces, or wall cavity.)

Check that Fiber GlassI flexible duct and ductboard is in good condition (i.e., free of tears and abrasions; well adhered to underlying materials)?Are interior ductwork surfaces free of visible debris? Is the supply air plenum (directly downstream of the air handling unit) free of moisture stains and contaminants? Is the return air plenum free of visible dust or debris? Do filters fit properly and are they the proper efficiency as recommended by HVAC system manufacturer? Are the blower blades clean and free of oil and debris? Is the blower compartment free of visible dust or debris? Did the service provider obtain access to and clean the entire heating and cooling system, including ductwork, drain pans, dehumidifiers, coils, secondary drain pans, fans, heating elements, access doors. Are the registers, grilles, and diffusers visibly clean? Have all registers, grilles, and diffusers been firmly reattached? Does the system function properly in both the heating and cooling modes after cleaning?Are newly installed access doors in sheet metal ducts attached with more than just duct tape (e.g., screws, rivets, mastic, etc.)? With the system running, is air leakage through access doors or covers very slight or non-existent?Are both sides of the cooling coil visibly clean? If you point a flashlight into the cooling coil, does light shine through the other side? It should if the coil is clean. Are the coil fins straight and evenly spaced (as opposed to being bent over and smashed together)? Is the coil drain pan completely clean and draining properly?

How to Prevent Duct Contamination

Whether or not you decide to have the air ducts in your home cleaned, committing to a good preventive maintenance program is essential to minimize duct contamination.

Controlling moisture can often be difficult, but here are some steps you can take:

Moisture can enter a system through leaks or if the system has been improperly installed or serviced. Research suggests that condensation (which occurs when a surface temperature is lower than the dew point temperature of the surrounding air) on or near cooling coils of air conditioning units is a major factor in moisture contamination of the system. The presence of condensation or high relative humidity is an important indicator of the potential for mold growth on any type of duct. To prevent moisture:

1. Promptly and properly repair any leaks or water damage. Pay particular attention to cooling coils, which are designed to remove water from the air and can be a major source of moisture contamination of the system that can lead to mold growth. Make sure the condensate pan drains properly. The presence of substantial standing water and/or debris indicates a problem requiring immediate attention. Check any insulation near cooling coils for wet spots.
2. Make sure ducts are properly sealed and insulated in all non-air-conditioned spaces (e.g., attics and crawl spaces). This will help to prevent moisture due to condensation from entering the system and is important to make the system work as intended. To prevent water condensation, the heating and cooling system must be properly insulated.
3. If you are replacing your air conditioning system, make sure that the unit is the proper size for your needs and that all ducts are sealed at the joints. A unit that is too big will cycle on and off frequently, resulting in poor moisture removal, particularly in areas with high humidity. Also make sure that your new system is designed to manage condensation effectively.